1. Field of the Invention
The invention relates to an energy-absorbing bumper or fender for protecting ships, barges or other floating vessels, or docking structure for such vessels, from damage when such vessels are tied up at or docking at such docking structure, for example at offshore oil rig structures or barge loading platforms. More particularly the invention relates to an improved tire device to be stacked rotatably on an upright metal bumper pipe mounted on an offshore rig structure and the like. Finally, the invention relates to a cured-in-tire elastomeric polyurethane or rubber foam-filled vehicle tire used as a rotatable energy-absorbing ring or sleeve for ship bumpers.
2. Description of the Prior Art
Many different types and kinds of energy-absorbing bumper devices are known in the prior art for protecting ships or other floating vessels and the structures at which such vessels are docked from damage due to relative movement between the vessel and the dock structure. Particularly in offshore oil rig structure installations, bumpers formed by an upright metal pipe mounted on a leg or other structural member of the rig surrounded by a stack of rubber rings, tires or the like have been used. Other forms of fenders using tires as the energy-absorbing device either unfilled or filled have also been used. Examples of such prior art structures are shown in U.S. Pat. Nos. 2,562,957, 2,952,979 and 4,005,672.
Used auto and truck tires comprise a relatively inexpensive source of energy-absorbing elastomeric material for bumpers but problems have arisen in their use stacked on an upright metal bumper pipe including as many as twenty or more tires which each may have an axial thickness of from nine to twelve inches.
Such used tires, when hollow, may be readily damaged or ripped from the bumper pipe when a rib of a ship docked at a structure wedges between adjacent stacked bumper tires and moves up and down as a result of wave action. Unsuccessful attempts have been made to provide some filling material in a tire cavity, such as suggested in the boat fender of U.S. Pat. No. 2,952,979, when used vehicle tires are available or used stacked on a vertical rig structure bumper to prevent collapse of the tire carcass walls when forcefully engaged by a ship moving relative to the bumper.
Vehicle tires, frequently in recent years, for off-the-road vehicles of the pneumatic tire shape and type have been filled when mounted on a rim completely with various resilient or void-free elastomeric materials to prevent the tires from going flat, by being punctured or torn by sharp objects encountered when a vehicle equipped with such tires travels in areas such as metal scrap yards. For example, see U.S. Pat. Nos. 867,600, 3,866,652 and Re. 29,890. Such rim-mounted filled vehicle tires for vehicle use, however, are not feasible for use in the assembly of ship bumpers for a variety of reasons.
First of all, the cost of such filled vehicle tires is economically prohibitive for use stacked in large numbers as a part of a bumper assembly.
Next, the weight of the metal rims of such filled vehicle tires stacked in large numbers as a part of a ship bumper assembly cannot be tolerated. Such weight would add considerably to the structural strength requirements of the rig structure itself.
Further, the weight of the resilient or void-free elastomeric material filling the rim-mounted vehicle tires also substantially exceeds the preferred limits of weight for rotatable energy-absorbing bumper ring members.
Accordingly, a need has long existed for a rotatable energy-absorbing ring or sleeve unit for ship bumpers composed of relatively inexpensive vehicle tires free of rims and completely filled with an extremely lightweight energy-absorbing strong elastomeric foam material such as polyurethane foam or rubber foam.